1. Field of the Invention
The present invention relates to a production method and a production apparatus for a ceramic green sheet for use in a ceramic electronic part comprising a circuit of an electronic appliance.
2. Description of the Related Art
Conventionally, a ceramic green sheet for use in a ceramic electronic part, represented for instance by a laminated capacitor, a laminated inductor, a laminated LC filter and a multi-layer substrate, has been produced with known production apparatus by kneading a mixture of an aqueous or organic solvent wherein ceramic powders such as barium titanate and ferrite are dissolved and a polymeric binder such as polymethyl methacrylate (PMMA), polyvinyl butylal (PVB) and polyvinyl alcohol (PVA) with a high speed mixer or a ball mill, applying the obtained ceramic slurry onto the surface of a carrier sheet such as a polyethylene terephthalate (PET) film at a thickness of several hundred .mu.m to several ten .mu.m thickness by a doctor blade method or a rolling method, drying and winding the same.
FIG. 1 is a configuration diagram of a production apparatus for a ceramic green sheet used in a conventional method of producing a ceramic green sheet. As shown in FIG. 1, a carrier sheet 51 applied with a liquid mold releasing agent is sent out from a dispatch part 52 and is placed between a pair of roller parts 53a, 53b so as to be moved horizontally. The surface 511 of the carrier sheet 51 has a ceramic slurry 55 applied from an applying part 54 when it passes immediately below the applying part 54. The ceramic slurry 55 can be obtained by adding a polymer binder into an aqueous or organic solvent with ceramic powders dispersed therein and kneading as mentioned above. The applying part 54 is provided with a doctor blade 57 at a height set with respect to a base part 56 for supporting the rear surface 512 of the carrier sheet 51 so that the thickness of the ceramic slurry 55 on the surface of the carrier sheet 51 can be made homogeneous by evening the ceramic slurry 55 on the surface 511 of the carrier sheet 51 with the doctor blade 57. Then, the ceramic slurry 55 on the surface 511 of the carrier sheet 51 is dried sufficiently while passing immediately below a drying part 58, and is taken up by a winding part 60 as a ceramic green sheet 59 with the carrier sheet 51 as shown in a broken circle in FIG. 1.
Although it is not shown in the figure, the taken-up ceramic green sheet 59 with the carrier sheet 51 is rewound, cut in a desired width, and the ceramic green sheet is removed from the carrier sheet 51. After forming an electrode pattern by printing a conductive paste on these ceramic green sheets by a screen printing method, a heat and pressing treatment is applied to a plurality of laminated ceramic green sheets so as to obtain a ceramic laminated product. By baking a ceramic laminated product accordingly obtained, and forming an external electrode at the end part, a ceramic electronic part can be obtained.
As mentioned above, a ceramic slurry obtained by kneading a mixture of an aqueous or organic solvent with ceramic powders dispersed therein and a polymer binder, is used in the conventional method of producing a ceramic green sheet.
When an aqueous solvent is used, although a means for preventing an explosive shock is not required in the drying part for drying the ceramic slurry, a problem is involved in that the polymer binder cannot be dispersed well in water, and thus it exists in the state of fine particles, and it is difficult to have a formed ceramic green sheet with a homogeneous density, and thus it is not suitable for achieving a thin ceramic green sheet.
When an organic solvent is used, although the binder can be dispersed well, and thus it is easy to achieve a thin ceramic green sheet, a problem is involved in that a means for preventing an explosive shock is required in the drying part for drying a ceramic slurry, and thus expensive production equipment is needed.